Electron microscope



Patented Dec. 30, 1941 `Bodo von Berries Aand Ernst Ruska, Berlin--v Spandau, Germany, assignors to Fides Gesellschaft fr die Verwaltung und Verwertung von gewerblichen Schutzrechten mit beschrnkter rmany, a corporation of Haftung, Berlin, Ge

Germany Application August .17, 193s, serial1ra/225,278` In Germany August 17, 1937 6 claims. (ci. 25o-ias) i This invention relates to electron microscopes and consists in means for adjusting the object very exactly with respect to theobjective.

According to the invention, the ydischarge vessel of an electron microscope is subdivided in the neighborhood of the object, and the two parts of the vessel are displaceable relative to each other and at right angles to the axis of the electron beam, roller-shaped bodies being provided'to absorb the forces created between these parts by the vacuum. It is thus possible to adjust very accurately the part carrying the object with respect to that carrying the objective, since the roller-shaped pressure bodies only negligibly hinder a displacement of the vtwo movable parts with respect to one another. This displacement will also not be affected if the object -is intensely cooled (for instance, with liquid air), since between the two opposite surfaces lying directly upon each other no grease film is interposed which would solidify at the low temperature.. A practical embodiment of -the invention is illustrated in the accompanying drawing in semi-diagrammatic form, in which- Fig. 1 represents a central sectional elevationof the portion of the microscope embodying the invention.

Fig. 2 represents a plan view of Fig. 1.

Fig. 3 represents in sectional elevation the adjusting screw I6 and its support, and

Fig. 4 represents a bottom view of sluice I in Fig. 1.

Referring to Fig. '1, I designates the objectcarrying member of an electron microscope. The central bore I of this member forms part of the evacuated discharge Vessel of the microscope and is arranged so as to -form a passage for the beam of electron rays which issue `from a cathode (not illustrated) in the direction of the arrow IIl. The member I is designed as a sluice in order to permit the insertion of objects into the path of the electron rays While the interior of the microscope remains evacuated. To this end, the member I has a transverse bore 2 for the reception of a plug or cock into the lateral bore of which the object may be inserted and which allows bringing the object to point 3. This plug structure is not shown here, as its construction does not form part of the present invention proper. A suitable sluice is illustrated and described in the copending application of Heinz Otto Mller, Serial No. 225,915.

The second relatively movable part or member of the electron microscope comprises a magnetic rest on the plate 4.

electron` beam. The upper surface of this second Vmember is formed by a plate which forms part of the ferromagnetic enclosure offa magnet coil .6 and abuts against the vacuum-tight tubu- -4 lar wall portion 510i the dischargevessel, this wall, portion being non-magnetic. The pole pieces "I and 8 of the magnetic lens are threaded into the tubular wall portion 5. 9 represents a cooling chamber for cooling ,the coil 6, andvg a nipple for supplying the cooling fluid.

Thebeam of electron rays `afterhaving passed through member I and through the object 1go-.A cated at point 3, passes Ythrough the central apertures of the pole pieces 'I and-8 and thencedirectly or. after being subjected to a further electron-optical' bias, onto a sur-face or electrode j so as to produce an enlarged image of the object. The other parts -of the-microscope are of common and well-known type, and, for the sake` of clearness, are omitted inthe drawing.

Several, preferably three,.pressure sustaining bodies Vare arranged betweenthe sluice carrier I andthe plate 4. In the embodiment shown steel balls II `are employed for this purpose which are mounted Vat both sides on polished; steel or agate plates I2 and I3. 'I'he diameter of thesepressure bodies is so chosen that the ground surface of member I does not directly In this manner a sliding friction is prevented between these parts. To seal the ,gap between the sluice carrier I and the plate 4 the flanged rubber cuff I4 is provided which is secured to the carrier with the aid of binding kwire and to the plate 4 by means Aof a liange I5. Since the lateral adjustments of sluice carrier I are only veryslight, the yield of cull I4 is sufficient to permit this. The sluicev carrier with its object 3 is adjusted withrespect to the magnetic lens '1, 8 b y means of the screws I6, I'I and I8 spaced 120 from one another-as carrier I with the aid of a resilient member I9 so as to permit slight adjustments of screws I6 and I'I without backing up or advancing screw I8. The pressure screws I6 and Il, which engage the sluice carrier directly, are as shown in Fig. 3 preferably provided with a steel ball 2l] at their ends which bears against a small agate plate ZI set into the sluice carrier I as shown in detail in Fig. 3.

In order to improve the communication between the two vacuum chambers lying at both lens system for electron-optically biasing the sides -of the object the sluice carrierl is promentioned ducts be arranged symmetrically to K the axis of the discharge device.

In order to cool the objecta cooling duct` 26 having the form shown in Fig. 4 and which partly surrounds the bore 24 is provided in the sluice carrier I. The cooling duct is preferably produced in such a manner that iirst a groove of suitable form is milled into the lower face of the sluice which is then closed by a plate 21 soldered thereto. The ends of the cooling duct 26 are provided-With nipples, such as nipple 26 shown in Fig. 1, to be connected with iiuid supply conduits. f

Electron microscopes according to the invention allow very fine adjustments of the object relative to the electron-optical axis of the electron beam in any direction transverse to this axis.

What is claimed is:

1. In an electron-optical device having means for holding an object and lens means for electron-optically producing an image of said object, in combination, a vacuum vessel having a vessel portion for accommodating said holding meansk with part of said holding means disposed exteriorly of said vessel, and another vessel portion containing said lens means with part of said lens means disposed exteriorly of said vessel, said vessel being subdivided transversely with respect to the electron-optical axis and between said two vessel portions, and said vessel portions being transversely movable relative to each other, and mechanical adjusting means connected-between said exteriorly disposed parts of said vessel portions for changing and fixing the relative position of said vessel portions.

2. In a microscopic device-having means for holding an object in Ythe path of a corpuscular beam, and lens means for electron-optically biasing said beam, in combination, av vacuum vessel having two adjoining vessel portions movable relative to each other along a plane transverse to said beam path, one of said vessel portions being designed for accommodating said objectholding means and said other vessel portion being rmlyconnected withl said lens means, a cuff of yielding material arranged concentrically to said path and connected with said two vessel portions to provide a gas-tight seal, antifriction means arranged between said portions and within said cuff, and means for adjusting said poraccesso tions relative to each other in any direction of said plane.

3. In a microscopic device having means for holding an object in the path of a corpuscular beam, ajyzi'dlenvs'ieans for electron-optically biasing said beam, in combination, a vacuum vessel subdivided so as to form two vessel portions, the plane of division extending close to the object and transversely with respect to said beam path, said two'vessel portions being movable relative to each-'otherjinidifferent directions along said plane-ofdivision,lgastight sealing means of yielding` type tlisp'osed at the junction of said vesselA portion three adjusting screw means spaced circumferentially and mounted on one of lsaid vessel'portions so as to bear against said other vessel-portion, none of said screw means including a bearing yielding towards the two other adjusting means,

4. Ina'microscopic device having means for holding anfobject in the path of a corpuscular beam, and lens means for electron-optically biasing saidlceam;A incombination, a vacuum vessel having two adjoining vessel portions movable relative yto; each, other along a plane transverse to said beam,path,.one of said vessel portions forming the stationary member of a cock-type sluicing` ,device for receiving said object-holding means,y and said other vessel portion being associated withr said lens means, said two vessel portions having coaxial central bores, respectively, forming; a passage for said beam and communicating lateral rbypass ducts for equalizing pres-4 forming a passage for said beam, a lateral bypass duct and a cooling duct, said axial borev and saidy by-pass ycluctcommunicating with the vacuum in saidl other vessel portions, and said cooling ductseparated from` .said vacuum andv arranged so as to vsubstantially surround said axial bore close to the place of said object,vand means for passing cooling agentfrom the outside of saidvessel -`through said cooling duct.

6. An apparatus as set forth in claim 1J wherein antifriction fmieansv and resilient tightening means aredisposed between said two vessel portions.

Bono v. BoRRIEs.

ERNST RUSKA. 

